<script type="text/javascript">
  // 1. alert()
  alert("Hello Java script");

  // 2. document.write()
  document.write("Message by Document Write");

  // 3. confirm()
  confirm("Are you sure to delete?");

  // 4. console.log()
  console.log("Press F12 On firefox and check this message in console tab");
</script>
